Chapter 18 Myofascial Pain Flashcards
Myofascial pain disorders
heterogeneous group of
clinical entities that share features that originate from
soft tissue pain with resultant regional symptomatology
Examples of Myofascial Pain Disorders
episodic tension-type headache, myofascial pain syndrome, temporomandibular disorder, muscle cramps, and low back pain
Muscle pain is thought to occur by two main mechanisms:
peripheral and central
Peripheral factors of muscle pain
trauma, dysregulated deep-tissue microcirculation, and altered muscular metabolism and mitochondrial function. Mechanical, thermal, or chemical stimulation can lead to activation of intramuscular group III and group IV nociceptors, which in turn give rise to an inflammatory cascade mediated by immune cells, leading to further recruitment
of inflammatory cells and propagation of local inflammation and sensitization
Central factors of muscle pain
Pain transmission occurs along
Ad and C-fibers into the inner lamina of the spinal cord, where complex changes occur, leading to sensitization and
chronic pain. Continuous nociceptive input via these pathways can lead to central sensitization of higher-order neurons, –> enhanced sensitivity to painful stimuli via
excitatory glutamate and aspartate-related neurotransmitter release (hyperalgesia),reduced thresholds to nonpainful stimuli (allodynia), and increased receptive fields, causing referred pain
Supraspinal mechanisms contribute to chronic muscular pain states include
decreased cerebral activity, hippocampal suppression, and possibly impaired stress responses. Once central sensitization occurs, pain becomes autonomous from sensory input from the affected
muscle(s)
The International Headache Society classifies tension-type
headaches (TTHs) as
infrequent episodic (,12 days/yr), frequent episodic (12 to fewer than 180 days/yr), and chronic (180 days/yr).
Pathophysiologic mechanisms responsible for TTH can be divided into
peripheral and central causes
Peripheral factors of tension-type headaches
Peripheral mechanisms are demonstrated by increased tenderness of pericranial myofascial tissue and increased electromyographic
and algometric pressure recordings
Central factors of tension-type headaches
Continuous nociceptive
input can lead to central sensitization, thereby converting episodic TTH into chronic headaches
Temporomandibular disorder (TMD)
is a broad term used to describe conditions arising in the jaw joint, muscles of mastication, and associated craniofacial structures. These conditions most commonly include pain, dysfunction, arthritis, and internal derangement
In patients with TMD Electromyographic recordings have demonstrated
altered muscular contraction,
as well as increased muscular tone
myofascial pain syndrome (MPS) characterizes by the
presence of loci of hypersensitivity within a tender, taut, palpable band of
muscle called a trigger point (TP)
trigger point
TPs are characterized by
referred pain on palpation and elicitation of a local twitch
response (LTR) with application of mechanical pressure
Trigger points can be classified into
active TPs or latent TPs.
Active TPs are described as pain in a motor locus
associated with spontaneous electrical activity, whereas
the more common latent TPs do not cause spontaneous
pain, but can be triggered by factors such as mechanical
stressors, dysfunctional postures, changes in weather, and either excessive immobility or the exaggerated use of muscles
What leads to the formation of a TP circuit?
It has been suggested that a positive feedback
cycle involving disproportionate acetylcholine release, sarcomere shortening, and increased concentrations of sensitizing substances leads to the formation of a TP circuit,
which upon connection with other spinal dorsal horn
neuronal pathways, activates latent TPs to become an
active TP
Spine structures functions,
protecting the spinal cord, maintaining posture and truncal stability, and acting as a steadying force for movement of the extremities.
Skeletal and ligamentous
structures serve as a
protective foundation from which attached muscles provide functional motor control, flexibility, and movement coordination
Weakness in the core muscles
(lumbo-pelvic-hip complex), unbalanced gait mechanics,
or dysfunctional muscular proprioception can
lead to
tears, strains, sprains, or spasm within the paraspinal musculature
True muscle cramps
painful involuntary skeletal
muscle contractions associated with electrical activity. EMG studies show fast rates of repetitive firing of motor units in affected muscles. True muscle cramps occur in the absence of fluid or electrolyte imbalance,
True muscle cramps are
more commonly found in patients with
well-developed muscles, in the third trimester of pregnancy, and in metabolic disorders such as cirrhosis and renal disease
causes of muscle cramps include
medications, lower motor neuron disease, hypothyroidism, and hereditary
disorders
Painful cramps can often be terminated by
stretching the cramped muscle.
Tricyclic antidepressants (TCAs)
amitriptyline, nortriptyline,
desipramine, and imipramine
